Question

5. Lasers used to cut metal can create an electric field of 2.66 106 N/C with a beam radius of 130 μm.

a) What is the size of the magnetic field created by this laser?

b) What is the intensity of this laser?

c) What is the laser’s power?

d) How much force is exerted due to radiation pressure?

6. What type of device uses induction to change the voltage of an electrical signal?

a) Electric Motor

b) Electric Generator

c) Transformer

d) Inductor

7. In which AC circuit does the voltage always lead the current by 90° (positive π/2 phase)?

a) capacitor

b) resistor/capacitor

c) inductor

d) resistor/inductor

Answer 1

5.(a) The size of the magnetic field created by this laser (B) will be

E = electric field = 2.66 x 106 N/C and c is the speed of light in vacuum = 299792458 m/s, Therefore,

5.(b) The intensity of the laser will be

is the free space permeability.

5.(c) The laser power (W) will be considering the beam radius as r

5.(d) The force will be

6. (3) Answer will be transformer. In transformer, the voltage can be increased or decreased by changing the number of turns in the primary or secondary coil using the principle of mutual induction between two coils.

7. (d) Answer will be resistor/inductor.

In resistor/inductor AC circuit, the voltage always lead the current by 90° (positive π/2 phase). Because the relation between the current and voltage across the inductor is given by